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Geographic isolation and climatic variability contribute to genetic differentiation in fragmented populations of the long-lived subalpine conifer Pinus cembra L. in the western Alps.
BMC Evolutionary Biology ( IF 3.4 ) Pub Date : 2019-10-17 , DOI: 10.1186/s12862-019-1510-4
Endre Gy Tóth 1, 2 , Francine Tremblay 1 , Johann M Housset 3, 4, 5 , Yves Bergeron 1, 3 , Christopher Carcaillet 4, 6
Affiliation  

BACKGROUND Genetic processes shape the modern-day distribution of genetic variation within and between populations and can provide important insights into the underlying mechanisms of evolution. The resulting genetic variation is often unequally partitioned within species' distribution range and especially large differences can manifest at the range limit, where population fragmentation and isolation play a crucial role in species survival. Despite several molecular studies investigating the genetic diversity and differentiation of European Alpine mountain forests, the climatic and demographic constrains which influence the genetic processes are often unknown. Here, we apply non-coding microsatellite markers to evaluate the sporadic peripheral and continuous populations of cembra pine (Pinus cembra L.), a long-lived conifer species that inhabits the subalpine treeline ecotone in the western Alps to investigate how the genetic processes contribute to the modern-day spatial distribution. Moreover, we corroborate our findings with paleoecological records, micro and macro-remains, to infer the species' possible glacial refugia and expansion scenarios. RESULTS Four genetically distinct groups were identified, with Bayesian and FST based approaches, across the range of the species, situated in the northern, inner and south-western Alps. We found that genetic differentiation is substantially higher in marginal populations than at the center of the range, and marginal stands are characterized by geographic and genetic isolation due to spatial segregation and restricted gene flow. Moreover, multiple matrix regression approaches revealed effects of climatic heterogeneity in species' spatial genetic pattern. Also, population stability tests indicated that all populations had experienced a severe historical bottleneck, no heterozygosity excess was detected, suggesting that more recently population sizes have remained relatively stable. CONCLUSIONS Our study demonstrated that cembra pine might have survived in multiple glacial refugia and subsequently recolonized the Alps by different routes. Modern-day marginal populations, at the edge of the species' range, could maintain stable sizes over long periods without inbreeding depression and preserve high amounts of genetic variation. Moreover, our analyses indicate that climatic variability has played a major role in shaping differentiation, in addition to past historical events such as migration and demographic changes.

中文翻译:

地理隔离和气候变异性有助于在阿尔卑斯山西部长寿命的亚高山针叶树Pinus cembra L.的零散种群中进行遗传分化。

背景技术遗传过程影响着种群内部和种群之间遗传变异的现代分布,可以为进化的潜在机制提供重要的见识。所产生的遗传变异通常在物种分布范围内分配不均,尤其是在范围极限处可能会表现出很大的差异,在这种范围内,种群的分裂和隔离在物种生存中起着至关重要的作用。尽管进行了一些分子研究,以研究欧洲高山高山森林的遗传多样性和分化,但影响遗传过程的气候和人口限制因素通常是未知的。在这里,我们应用非编码微卫星标记来评估零星的周边和连续种群的Cembra松树(Pinus cembra L.),一种长寿的针叶树种,它居住在阿尔卑斯山西部的亚高山树林过渡带中,以研究遗传过程如何促进现代空间分布。此外,我们用古生态记录,微观和宏观遗迹来证实我们的发现,以推断该物种可能的冰川避难所和扩张情景。结果使用贝叶斯和基于FST的方法,确定了四个遗传上不同的组,它们位于该物种的整个范围内,分别位于北部,内部和西南阿尔卑斯山。我们发现边缘人群的遗传分化显着高于该范围的中心,边缘种群的特征是由于空间隔离和基因流受限而地理和遗传隔离。而且,多元矩阵回归方法揭示了气候异质性对物种空间遗传模式的影响。另外,种群稳定性测试表明所有种群都经历了严重的历史瓶颈,未检测到杂合度过高,这表明最近的种群规模仍保持相对稳定。结论我们的研究表明,松柏松可能在多处冰川避难所中幸存下来,并随后通过不同途径重新定居了阿尔卑斯山。在物种范围边缘的现代边缘种群可以长期保持稳定的大小,而不会引起近亲衰退,并保留了大量的遗传变异。此外,我们的分析表明,气候变化在影响差异化方面发挥了重要作用,
更新日期:2019-10-17
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